Projecting a weary sense of frustration rather than outright moral indignation, Emanuel said, "You can make progress," citing the lowered murder rates and shooting incidents citywide in February and early March. "And then you get a senseless, despicable act of violence like this that is just heartbreaking."

Emanuel said the incident transcended any national sense of outrage about Chicago's gun violence.

"It's not about image," he said. "This was a child, 6 months."

He did not even rise to questions raised about whether the baby's father, Jonathan Watkins, was cooperating with police, saying he'd leave that to law-enforcement officials and calling on citizens to come forward with information to "catch the murderer."

Instead, he focused on the safety of all city children.

"The child is truly innocent," Emanuel said. "Everybody has a role to play to make sure every child is in a safe city, in a safe neighborhood, in a safe community, on a safe street.

"I will not rest until every child grows up in that environment," Emanuel added.

Emanuel made the remarks at a Homan Square Park news conference celebrating a "Summer of Learning" initiative to keep Chicago children learning throughout the summer at various citywide community and civic organizations and cultural institutions.